Defines a monitor MBean designed to observe the values of a gauge attribute.

A gauge monitor observes an attribute that is continuously
variable with time. A gauge monitor sends notifications as
follows:

if the attribute value is increasing and becomes equal to or
greater than the high threshold value, a threshold high
notification is sent. The notify high flag must be set to
true.
Subsequent crossings of the high threshold value do not cause
further notifications unless the attribute value becomes equal to
or less than the low threshold value.

if the attribute value is decreasing and becomes equal to or
less than the low threshold value, a threshold low
notification is sent. The notify low flag must be set to
true.
Subsequent crossings of the low threshold value do not cause
further notifications unless the attribute value becomes equal to
or greater than the high threshold value.

This provides a hysteresis mechanism to avoid repeated triggering
of notifications when the attribute value makes small oscillations
around the high or low threshold value.

If the gauge difference mode is used, the value of the derived
gauge is calculated as the difference between the observed gauge
values for two successive observations.
The derived gauge value (V[t]) is calculated using the following method:

V[t] = gauge[t] - gauge[t-GP]

This implementation of the gauge monitor requires the observed
attribute to be of the type integer or floating-point
(Byte, Integer, Short,
Long, Float, Double).